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CVE-2021-47221 (GCVE-0-2021-47221)

Vulnerability from cvelistv5 – Published: 2024-05-21 14:19 – Updated: 2026-05-11 13:50
VLAI
Title
mm/slub: actually fix freelist pointer vs redzoning
Summary
In the Linux kernel, the following vulnerability has been resolved: mm/slub: actually fix freelist pointer vs redzoning It turns out that SLUB redzoning ("slub_debug=Z") checks from s->object_size rather than from s->inuse (which is normally bumped to make room for the freelist pointer), so a cache created with an object size less than 24 would have the freelist pointer written beyond s->object_size, causing the redzone to be corrupted by the freelist pointer. This was very visible with "slub_debug=ZF": BUG test (Tainted: G B ): Right Redzone overwritten ----------------------------------------------------------------------------- INFO: 0xffff957ead1c05de-0xffff957ead1c05df @offset=1502. First byte 0x1a instead of 0xbb INFO: Slab 0xffffef3950b47000 objects=170 used=170 fp=0x0000000000000000 flags=0x8000000000000200 INFO: Object 0xffff957ead1c05d8 @offset=1496 fp=0xffff957ead1c0620 Redzone (____ptrval____): bb bb bb bb bb bb bb bb ........ Object (____ptrval____): 00 00 00 00 00 f6 f4 a5 ........ Redzone (____ptrval____): 40 1d e8 1a aa @.... Padding (____ptrval____): 00 00 00 00 00 00 00 00 ........ Adjust the offset to stay within s->object_size. (Note that no caches of in this size range are known to exist in the kernel currently.)
Severity
No CVSS data available.
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-06-17 17:38 UTC
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 89b83f282d8ba380cf2124f88106c57df49c538c , < f6ed2357541612a13a5841b3af4dc32ed984a25f (git)
Affected: 89b83f282d8ba380cf2124f88106c57df49c538c , < ce6e8bee7a3883e8008b30f5887dbb426aac6a35 (git)
Affected: 89b83f282d8ba380cf2124f88106c57df49c538c , < e41a49fadbc80b60b48d3c095d9e2ee7ef7c9a8e (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.7
Unaffected: 0 , < 5.7 (semver)
Unaffected: 5.10.46 , ≤ 5.10.* (semver)
Unaffected: 5.12.13 , ≤ 5.12.* (semver)
Unaffected: 5.13 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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      "containers": "{\"adp\": [{\"title\": \"CVE Program Container\", \"references\": [{\"url\": \"https://git.kernel.org/stable/c/f6ed2357541612a13a5841b3af4dc32ed984a25f\", \"tags\": [\"x_transferred\"]}, {\"url\": \"https://git.kernel.org/stable/c/ce6e8bee7a3883e8008b30f5887dbb426aac6a35\", \"tags\": [\"x_transferred\"]}, {\"url\": \"https://git.kernel.org/stable/c/e41a49fadbc80b60b48d3c095d9e2ee7ef7c9a8e\", \"tags\": [\"x_transferred\"]}], \"providerMetadata\": {\"orgId\": \"af854a3a-2127-422b-91ae-364da2661108\", \"shortName\": \"CVE\", \"dateUpdated\": \"2024-08-04T05:32:07.427Z\"}}, {\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2021-47221\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2024-06-17T17:38:07.843861Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2024-06-17T17:38:09.016Z\"}}], \"cna\": {\"title\": \"mm/slub: actually fix freelist pointer vs redzoning\", \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"89b83f282d8b\", \"lessThan\": \"f6ed23575416\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"89b83f282d8b\", \"lessThan\": \"ce6e8bee7a38\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"89b83f282d8b\", \"lessThan\": \"e41a49fadbc8\", \"versionType\": \"git\"}], \"programFiles\": [\"mm/slub.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"5.7\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"5.7\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"5.10.46\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.12.13\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.12.*\"}, {\"status\": \"unaffected\", \"version\": \"5.13\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"mm/slub.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/f6ed2357541612a13a5841b3af4dc32ed984a25f\"}, {\"url\": \"https://git.kernel.org/stable/c/ce6e8bee7a3883e8008b30f5887dbb426aac6a35\"}, {\"url\": \"https://git.kernel.org/stable/c/e41a49fadbc80b60b48d3c095d9e2ee7ef7c9a8e\"}], \"x_generator\": {\"engine\": \"bippy-c8e10e5f6187\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nmm/slub: actually fix freelist pointer vs redzoning\\n\\nIt turns out that SLUB redzoning (\\\"slub_debug=Z\\\") checks from\\ns-\u003eobject_size rather than from s-\u003einuse (which is normally bumped to\\nmake room for the freelist pointer), so a cache created with an object\\nsize less than 24 would have the freelist pointer written beyond\\ns-\u003eobject_size, causing the redzone to be corrupted by the freelist\\npointer.  This was very visible with \\\"slub_debug=ZF\\\":\\n\\n  BUG test (Tainted: G    B            ): Right Redzone overwritten\\n  -----------------------------------------------------------------------------\\n\\n  INFO: 0xffff957ead1c05de-0xffff957ead1c05df @offset=1502. First byte 0x1a instead of 0xbb\\n  INFO: Slab 0xffffef3950b47000 objects=170 used=170 fp=0x0000000000000000 flags=0x8000000000000200\\n  INFO: Object 0xffff957ead1c05d8 @offset=1496 fp=0xffff957ead1c0620\\n\\n  Redzone  (____ptrval____): bb bb bb bb bb bb bb bb               ........\\n  Object   (____ptrval____): 00 00 00 00 00 f6 f4 a5               ........\\n  Redzone  (____ptrval____): 40 1d e8 1a aa                        @....\\n  Padding  (____ptrval____): 00 00 00 00 00 00 00 00               ........\\n\\nAdjust the offset to stay within s-\u003eobject_size.\\n\\n(Note that no caches of in this size range are known to exist in the\\nkernel currently.)\"}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2024-11-04T11:37:02.712Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-47221\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2024-11-04T11:37:02.712Z\", \"dateReserved\": \"2024-04-10T18:59:19.529Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-05-21T14:19:27.553Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.1"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.